Mercury Cathode Research Articles

Electrochemical Reduction of Aromatic Diazonium Salts: I . Electrochemical Behavior of p‐Tolyl‐ and p‐Anisyldiazonium Fluoborates at a Mercury Cathode: Evidence for the Corresponding Hydrazines Formation

Reduction of p‐methyl and p‐methoxyphenyldiazonium fluoborate in aqueous solutions at mercury micro and macroelectrodes results in formation of a primary hydrazine . The radical . formed in the first electrochemical step forms Ar‐Hg‐Ar; the product of the two electrons reduction forms in competitive chemical reactions. Low temperature (4°C) and moderate stirring enable minimizing of these side reactions.

Multielement analysis of human blood serum by neutron activation and controlled potential electrolysis.

The combination of neutron activation analysis and controlled potential electrolysis has proved itself to be a useful multielement method for the determination of 14 elements in a 500-..mu..L sample of human blood serum. After freeze-drying and irradiation, the samples are decomposed and electrolyzed for 3 h. The radioactive species deposited on the mercury cathode allow simultaneous determination of eight elements (Ag, Au, Cd, Co, Fe, Hg, Sb, Zn). Another six elements (Br, Ca, Cs, Na, Rb, Sc) are determined by measuring the activities in the residual solution. Data illustrating the precision of the method are given. The determination limits are of the order 10/sup -1/-10/sup -3/ ..mu..g/L for the nine trace elements investigated.

Determination of aluminium in iron, steel and ferrous and non-ferrous alloys by atomic-absorption spectrophotometry after a mercury-cathode separation and extraction of the aluminium—acetylacetone complex

A method for determining 0.0005% or more of total aluminium in high- and low-alloy steels, iron and ferrovanadium is described. Iron, chromium and other matrix elements are separated from aluminium by electrolysis with a mercury cathode and aluminium is separated from tungsten, titanium, vanadium and phosphate by chloroform extraction of its acetylacetone complex at pH 6.5 from an ammonium acetate—hydrogen peroxide medium. The extract is evaporated to dryness and organic material is destroyed with nitric and perchloric acids. Aluminium is determined by atomic-absorption spectrophotometry in a nitrous oxide—acetylene flame, at 309.3 nm, in a 5% v/v perchloric acid medium containing 1000 μg of sodium per ml. Acid-soluble and acid-insoluble aluminium can also be determined. The method is also applicable to copper- and nickel-base alloys. Results obtained by this method are compared with those obtained spectrophotometrically with Pyrocatechol Violet, after the separations described above followed by the separation of the residual co-extracted iron and copper by a combined ammonium pyrrolidinedithiocarbamate—cupferron—chloroform extraction from 10% v/v hydrochloric acid medium.

Stereochemical studies of the electrolytic reactions of organic compounds—XVI. Electrolytic reduction of prochiral ketones having a chirality center at their β-positions to the corresponding diastereomeric alcohols

Prochiral ketones, which have a chirality center at their β-positions but are not optically-active, were electrolytically reduced at a mercury cathode. It is noticeable that the isomeric ratio of the diastereomeric secondary alcohols formed in the electroreduction was quite different from that in chemical reduction with lithium aluminum hydride. On the basis of stereochemical data obtained, stereochemical course for the reduction were discussed.

Electroreduction of substituents on a pyridine ring in aqueous sulfuric acid

Hydroxymethyl, aminomethyl, carboxyl, methoxycarbonyl, carbamoyl, hydrazinocarbonyl, formyl, vinyl and phenyl groups attached to various positions of a pyridine ring were reduced at a mercury cathode in an aqueous sulfuric acid solution. These groups, except for the phenyl group, at the 2- and 4-positions could be reduced, while the reduction of the groups at the 3-position seemed to be difficult. The reduction potential of the groups at the 4-position was generally less negative than that of the same group at the 2-position. Current efficiencies for the reduction of hydroxymethyl, aminomethyl and vinyl groups were higher in the case of 4-substituted-pyridines than 2-substituted-pyridines, while this tendency reversed in the case of the other groups. An obvious steric hindrance effect on the current efficiency was also observed in the reduction of substituted-hydroxymethyl groups attached to the 2-position. On the basis of these results, reduction mechanism is discussed and also the synthetic scope is described.

Electrochemical behavior of decyl mercuric halides at mercury cathodes in dimethylformamide

Polarograms for decyl mercuric halides in dimethylformamide containing tetraalkylammonium perchlorates exhibit two waves. When large-scale electrolyses of decyl mercuric halides are performed at potentials corresponding to the first polarographic wave, the couldometric n value is unity and didecylmercury is obtained in quantitative yield; electrolyses carried out at potentials on the plateau of the second polarographic wave afford only decane and the n value is essentially 2. Double-potential-step chronocoulometry and staircase voltammetry indicate that, at potentials corresponding to the first polarographic wave, the decyl mercuric halide (which is itself adsorbed onto mercury to the extent of less than a monolayer) undergoes reversible one-electron reduction to adsorbed decyl mercury radicals and to adsorbed decyl mercury radical “polymer”; the adsorbed radicals have a lifetime of approximately 10 −3 s and disproportionate into didecylmercury and elemental mercury. In the presence of electrolytically released halide ion, the adsorbed radicals are reoxidized to the decyl mercuric halide; alternately, the adsorbed species are reoxidized to decyl mercury cations at a potential approximately 600 mV more positive than that required for reoxidation to the decyl mercuric halide. At potentials corresponding to the second polarographic wave, reduction of decyl mercuric halides is an irreversible process producing decyl carbanions which are protonated by traces of water in the solvent to give decane.

Electrochemical behavior of decyl mercuric halides at mercury cathodes in dimethylformamide

Polarograms for decyl mercuric halides in dimethylformamide containing tetraalkylammonium perchlorates exhibit two waves. When large-scale electrolyses of decyl mercuric halides are performed at potentials corresponding to the first polarographic wave, the couldometric n value is unity and didecylmercury is obtained in quantitative yield; electrolyses carried out at potentials on the plateau of the second polarographic wave afford only decane and the n value is essentially 2. Double-potential-step chronocoulometry and staircase voltammetry indicate that, at potentials corresponding to the first polarographic wave, the decyl mercuric halide (which is itself adsorbed onto mercury to the extent of less than a monolayer) undergoes reversible one-electron reduction to adsorbed decyl mercury radicals and to adsorbed decyl mercury radical “polymer”; the adsorbed radicals have a lifetime of approximately 10 −3s and disproportionate into didecylmercury and elemental mercury. In the presence of electrolytically released halide ion, the adsorbed radicals are reoxidized to the decyl mercuric halide; alternately, the adsorbed species are reoxidized to decyl mercury cations at a potential approximately 600 mV more positive than that required for reoxidation to the decyl mercuric halide. At potentials corresponding to the second polarographic wave, reduction of decyl mercuric halides is an irreversible process producing decyl carbanions which are protonated by traces of water in the solvent to give decane.

Synthese asymetrique par voie electrochimique—VI. Etudes en double induction

The electrochemical reduction of (−) menthyl phenylglyoxylate is performed at a mercury cathode in the presence of various additional compounds. These compounds may be more or less adsorbed, chiral or not and more or less efficient as proton donating species. This study shows that optical yield depends on the working potential and the proton donating ability of the solution. Experimental results are in good agreement with the hypothesis of a kinetic competition between the electric field effects (inversion of the intermediate carbanion and its repulsion towards the solution) and protonation of this carbanion either in the near vicinity of the electrode or in the bulk of the solution.

Zur Reaktion aromatischer Phosphanderivate mit Elektronen, I. / On the Reaction of Aromatic Phosphane Derivatives with Electrons, I.

Abstract The compounds ;p-Me2P(X)-C6H4-P(X)Me2, X = O, S, Se, NPh undergo one-electron reduction at a mercury cathode or on reaction with solvated electrons in a K/18-crown-6/THF mixture. The radical anions formed are persistent and have been characterized by ESR. They may be described as complexes of the spin-bearing moiety p-Me2P-C6H4-PMe2 · with the coordinated groups X.

A new type of organic electrosynthesis reactor with a t wo-phase gas-electrolyte stream flowing through a mercury cathode. I. Application in electrochemical preparation of organotin compounds

An electrochemical technique is particularly convenient for the synthesis of hexabutyldistannane and hexaphenyldistannane. The reaction involved is the reduction of compounds of the type R3SnX dissolved in methanol. The conditions for preparative electrolysis were determined from a preliminary study of electrochemical kinetics. The technique employed permits continuous electropreparation and separation of these distannanes. In the reactor, an efficient renewal of the cathodic surface is obtained by passing the electrolytic solution, together with bubbled nitrogen, through the mercury pool. Results of electropreparation of distannanes in a large laboratory-scale apparatus are presented.

A rapid single‐step digestion procedure for the determination of N, P, K, Ca, & Mg in leaf tissues

Abstract Digestion of leaf tissues by chronic acid, without any externally applied heat, could be taken to completion when mineral‐free soluble starch is admixed with the sample. N, P and K in the resulting solution could be estimated without any necessity to remove the excess Cr present; if, however, Ca and Mg too need to be determined, then Cr could be quantitatively separated electrolytically with a mercury cathode, and all the 5 elements estimated in the clear, Cr‐free solution. Procedures for both types of analysis have been outlined, and the reliability of the analytical technique established statistically.

Preparation de pyrrolines N-oxydes, pyrrolines et pyrrolidines par reduction electrochimique de γ-nitrocetones

Judiciously selected conditions of controlled potential electrolysis, at a mercury cathode in aqueous organic media, of γ-nitroketones result in quantitative yields of 1-pyrroline 1-oxides, pyrrolines or pyrrolidines.

A new type of organic electrosynthesis reactor with a two-phase gas-electrolyte stream flowing through a mercury cathode, II. Limiting currents and mass-transfer studies in organotin electrosynthesis

A new electrochemical reactor involving a mercury cathode and a two-phase (gas-liquid) flow has been studied with a view to continuously manufacturing hexaphenyl and hexabutyldistannane b'y reduction of triorganotin chloride R3SnCl. In each case the interpretation of the determining step of the process is discussed after a study of the electrochemical kinetics. In the reactor an efficient renewal of the cathodic surface is obtained by passing the electrolysis solution together with nitrogen gas through the mercury pool. Results of mass transfer rate studies with the cell working either as a plug-flow reactor or as a continuously stirred reactor are compared for different gas and electrolyte flows. The experiments show that gas and electrolyte flows through a mercury pool offer attractive possibilities of application for large-scale preparative electrolysis, by solving simultaneously the problems of mass transport and electrode surface renewal.

Electrolytic reductive coupling. addition of perfluoroalkyliodides to alcenes

Abstract Addition of perfluoroalkyliodides (R F I) to alcenes has been and is extensively studied using radical initiators and UV light irradiation. In this work, the addition of R F I (R F = CF 3 (CF 2 ) n n = 4,6,8) to allylic and propargylic alcohol, and to diallyl ether is performed using and electrochemical initiation. Electrolysis is realised in two kinds of cell: 1. mercury cathode, DMF, LiClO 4 electrolyte. 2. fiber carbon cathode, water Kcl electrolyte. We obtain addition compounds and/or products resulting from the electrochemical increase of pH in the catholyte. When using an aqueous electrolyte, the organic phase is dispersed in water. This heterogeneous electrolysis appears as a very quick, high yield route, expected compounds being obtained in a pure phase. The mechanism observed when working with allylic alcohol is : The formation of the iodhydrine appears as resulting from a radical catalytic process initiated by the electrochemical reduction of R F I. When the organic phase (R F I + CH 2 = CH-CH 2 OH) is completely converted to iodhydrine, the electrolysis of the water phase produces an increase of pH in the catholyte. Consequently, the iodhydrine is converted to the epoxide: Similar reactions have been performed:

Reductive alkylation of 9:10 anthraquinone at mercury cathode

Reductive alkylation of 9:10 anthraquinone at mercury cathode

Electrolytical fission at mercury cathodes of an NO single bond in ethers derived from 1-hydroxybenzo( d)-1,2,3-triazoles

The single NO bond in various ethers derived from 1-hydroxybenzo( d)-1,2,3-triazoles is reduced at mercury cathodes in a 2-electron process giving rise to the non-substituted benzotriazole and a corresponding primary alcohol. Controlled-potential electrolysis actually resulted in isolating the products of the above type eg benzotriazole and 2-piperidinoethanol. Cathodic reduction of non-substituted benzotriazole in acid media proceeds evidently via a chemical reaction between benzotriazole and hydrogen obtained by the catalytic reduction of hydrogen ions at the mercury electrode.

The use of redox reactions in the analysis of dyes and dye intermediates: IX. The reductometric, polarographic, and coulometric determination of 4-nitrotoluene-2-sulfonic acid

The reduction of 4-nitrotoluene-2-sulfonic acid by chemical reaction with titanium(III) chloride and by electrochemical polarography and coulometry on a mercury cathode was studied. Conditions were found for the analytical application of these reactions.

The use of redox reactions in the analysis of dyes and dye intermediates: VIII. The determination of 4,4′-dinitrostilbene-2,2′-disulfonic acid by constant potential coulometry

The number of electrons exchanged in the electrochemical reduction of 4,4′-dinitrostilbene-2, 2′-disulfonic acid on a mercury cathode in Britton-Robinson buffer solution of pH 10 and in 0.1 M tetramethylammonium bromide solution was determined. A sensitive determination of the studied compound by constant potential coulometry was developed, and its accuracy and reproducibility were found.

The electrochemical preparation of 3-bromothiophen

The electrochemical reduction of 2,3,5-tribromothiophen to 3-bromothiophen may be carried out in good yield with a high current efficiency using a lead, mercury, zinc or graphite cathode in 70% dioxan/30% water containing sodium bromide (0.2 M) and a potential just positive to that for hydrogen evolution. The electrolysis may be designed to form free bromine at the anode or thiophen may be brominated in the anolyte; the product is 2-bromothiophen or 2,5-dibromothiophen which is resistant to further substitution in this solvent. Various strategies for the scale up of this synthesis are discussed.

Electroreduction of dinitrogen in a Ti(III)−Mo(III)-guanidine system

Dinitrogen reduction on a mercury cathode has been studied in an alkaline methanol solution with guanidine buffer (pK=13.6) in the presence of homogeneous catalysts (alkoxy complexes of Mo(III) and Ti(III). As is found, dinitrogen electroreduction occurs on the electrode surface. The reaction rate is determined by the rate of electron transfer.